Inflammatory myoglandular polyp has been characterized as a solitary, non-neoplastic polyp consisting of inflammatory granulation tissue in the lamina propria, proliferation of muscularis mucosae, and hyperplastic glands with variable cystic change (1-6). IMGP is solitary, pedunculated and, rarely, covered by a fibrin cap. Also, IMGP has no association with inflammatory bowel diseases and is located not only in the rectosigmoid, but also in the descending and transverse colon (7). In our case, the localization was in the sigmoid colon.
Although the etiology of IMGP remains uncertain, Nakamura (1) proposed that chronic trauma from intestinal persitalsis may contribute to the pathogenesis of IMGP. Since IMGP has never been reported to accompany neoplasia to date (1-6) endoscopic polypectomy alone seems to be sufficient treatment. However, our patient had a polyp that was too large for endoscopic removal, and we preferred surgery for this case. On the other hand, there has been controversy about whether IMGP is clinicopathologically distinct from mucosal prolapse syndrome, inflammatory cloacogenic polyp, inflammatory cap polyp, and polypoid prolapsing mucosal folds of diverticular disease (6). Many polypoid conditions throughout the gastrointestinal tract have been thought to be due to mucosal prolapse (8). Also, mucosal prolapse may be the etiological cause of myoglandular polyp. This entity bears similarity to polypoid prolapsing mucosal folds in diverticular disease as reported by Kelly (9). Nakamura pointed to the fact that patients who had myoglandular polyps usually had diverticuli in the sigmoid colon (1). In accordance with this report, our case had multiple diverticula in close proximity to the main pathology. IMGP was composed of inflammatory granulation tissue, hyperplastic glands, and proliferation of smooth muscle in a radial fashion but never showed the villous architecture usually found in the mucosal prolapse syndrome (10). Inflammatory cloacogenic polyp is a solitary, pedunculated polyp with tubulovillous architecture only at the anorectal transition zone (11). Also, it is known that inflammatory myoglandular polyp has to be distinguished from other polyps because of its different clinical features. Mucous diarrhea and tenesmus are the most common symptoms of patients with inflammatory cap polyp (12), while the main symptom of IMGP is hematochezia (1-4). However, the causes of inflammatory myoglandular polyp are still obscure, and further accumulation of cases may disclose their pathogenesis.